POPULATION-CHANGES OF THE VERTEBRATE COMMUNITY DURING A SNOWSHOE HARECYCLE IN CANADA BOREAL FOREST

We measured the density changes of 22 species of vertebrates during a snowshoe cycle in northern Canada. Hares were the dominant herbivore i n the system and changes in their numbers were correlated with changes in numbers of arctic ground squirrel, spruce grouse, ptarmigan, lynx, coyote, great horned owl, goshawk, raven and hawk owl. Hare numbers w ere not correlated with numbers of red-backed vole which showed peaks during the low, increase, and early decline phases of the hare cycle. Hawk owls were the only predator whose numbers correlated with changes in red-backed voles while boreal owls and weasels were correlated wit h densities of Microtus. Red squirrel, American kestrel, red-tailed ha wk, northern harrier, wolverine, magpie, and gray jay showed no correl ation with hare or vole numbers. We conclude that species in the borea l forests of Canada do not exhibit the strong synchrony found between voles and other members of the vertebrate community in northern Fennos candia. We discuss some of the possible reasons for these differences.